Injection drug use is an increasingly-prevalent cofactor for HIV transmission in the United States, leading to increased rates of transmission into the heterosexual partners and marked increases in maternal-fetal transmission. During this FY, studies of model systems for syringe disinfection were completed that reveal persistence of HIV genetic material after syringe-washing procedures employed by experienced drug abusing research volunteer injection drug users (IDU volunteers). In analyzing data from viral load studies from a population of actively-self-administering IDU volunteers, high levels of circulating HIV-1 were detected in peripheral white blood cells and in plasma. Comparisons of detection techniques revealed that HIV capture/PCR displayed maximal sensitivity for detecting HIV-1 in the IDUs. These studies are being supplemented by studies of drug reward in individuals with HIV dementia/encephalopathy currently in planning stages.